Fungal diseases are common problems in crop agriculture. Many strides have been made against plant diseases as exemplified by the use of hybrid plants, pesticides and improved agricultural practices. However, as any grower or home gardener can attest, the problems of fungal plant disease continue to cause difficulties in plant cultivation. Thus, there is a continuing need for new methods and materials for solving the problems caused by fungal diseases of plants. These problems can be met through a variety of approaches. For example, the infectious organisms can be controlled through the use of agents that are selectively biocidal for the pathogens. Another method is interference with the mechanism by which the pathogen invades the host crop plant. Yet another method, in the case of pathogens that cause crop losses, is interference with the mechanism by which the pathogen causes injury to the host crop plant. Still another method, in the case of pathogens that produce toxins that are undesirable to mammals or other animals that feed on the crop plants, is interference with toxin production, storage, or activity. This invention falls into the latter two categories.
Since their discovery and structural elucidation in 1988 (Bezuidenhout S, Gelderblom W, Gorst-Allman C, Horak R, Marasas W, Spiteller B, Vleggaar R (1988) "Structure elucidation of the fumonisins, mycotoxins from Fusarium moniliforme." Journal Chem Soc, Chem Commun 1988: 743-745), fumonisins have been recognized as a potentially serious problem in maize-fed livestock. They are linked to several animal toxicoses including leukoencephalomalacia (Marasas W F O, Kellerman T S, Gelderblom W C A, Coetzer J A W, Thiel P (1988) "Leukoencephalomalacia in a horse induced by fumonisin B-1 isolated from Fusarium moniliforme." Onderstepoort Journal of Veterinary Research 55: 197-204; Wilson T M, Ledet A E, Owens D L, Rice L G, Nelson H A (1990) "Experimental liver disease in ponies associated with the ingestion of a corn-based ration naturally contaminated with fumonisin B.sub.1," American Association of Veterinary Laboratory Diagnosticians: Abstracts 33rd Annual Meeting, Denver, Colo., Oct. 7-9, 1990., Madison, Wis., USA) and porcine pulmonary edema (Colvin B M, Harrison L R (1992) "Fumonisin-Induced Pulmonary Edema and Hydrothorax in Swine." Mycopathologia 117: 79-82). Fumonisins are also suspected carcinogens. (Geary W (1971) Coord Chem Rev 7: 81; Gelderblom W C A, Kriek N P J, Marasas W F O, Thiel P G (1991) "Toxicity and Carcinogenicity of the Fusarium-Moniliforme Metabolite, Fumonisin-B1, in Rats." Carcinogenesis 12: 1247-1251; Gelderblom W C A, Semple E, Marasas W F O, Farber E (1992) "The Cancer-Initiating Potential of the Fumonisin-B Mycotoxins." Carcinogenesis 13: 433437). Fusarium isolates in section Liseola produce fumonisins in culture at levels from 2 to &gt;4000 ppm.(Leslie J, Plattner R, Desjardins A, Klittich C (1992) "Fumonisin B1 production by strains from different mating populations of Gibberella fujikoroi (Fusarium section Liseola)." Phytopathology 82: 341-345). Isolates from maize (predominantly mating population A ) are among the highest producers of fumonisin. kLeslie et al., supra). Fumonisin levels detected in field-grown maize have fluctuated widely depending on location and growing season, but both preharvest and postharvest surveys of field maize have indicated that the potential for high levels of fumonisins exists (Murphy P A, Rice L G, Ross P F (1993) "Fumonisin-B1, Fumonisin-B2, and Fumonisin-B3 content of Iowa, Wisconsin, and Illinois corn and corn screenings." J Agr Food Chem 41: 263-266). Surveys of food and feed products have also detected fumonisin (Holcomb M, Thompson H C Jr., Hankins L J (1993) "Analysis of fumonisin B-1 in rodent feed by gradient elution HPLC using precolumn derivation with FMOC and fluorescence detection." J Agr Food Chem 41: 764-767; Hopmans E C, Murphy P A (1993) "Detection of Fumonisin-B(1), Fumonisin-B(2), and Fumonisin-B(3) and hydrolyzed Fumonisin-B(1) in Corn-Containing foods." J Agr Food Chem 41: 1655-1658; Sydenham E W, Shephard G S, Thiel P G, Marasas W F O, Stockenstrom S (1991) "Fumonisin Contamination of Commercial Corn-Based Human Foodstuffs." J Agr Food Chem 39: 2014-2018). The etiology of Fusarium ear mold is poorly understood, although physical damage to the ear and certain environmental conditions can contribute to its occurrence (Nelson P E (1992) "Taxonomy and Biology of Fusarium moniliforme." Mycopathologia 117: 29-36). Fusarium can be isolated from most field grown maize, even when no visible mold is present. The relationship between seedling infection and stalk and ear diseases caused by Fusarium is not clear. Genetic resistance to visible kernel mold has been identified(Gendloff E, Rossman E, Casale W. Isleib T, Hart P (1986) "Components of resistance to Fusarium ear rot in field corn." Phytopathology 76: 684-688; Holley R N, Hamilton P B, Goodman M M (1989) "Evaluation of tropical maize germplasm for resistance to kernel colonization by Fusarium moniliforme." Plant Dis 73: 578-580), but the relationship to visible mold to fumonisin production has yet to be elucidated.
Fumonisins have been shown in in vitro mammalian cell studies to inhibit sphingolipid biosynthesis through inhibition of the enzyme sphinganine acyl transferase, resulting in the accumulation of the precursor sphinganine. (Norred W P, Wang E, Yoo X Riley R T, Merrill A H (1992) "In vitro toxicology of fuimonisins and the mechanistic implications." Mycopathologia 117: 73-78; Wang E, Norred W. Bacon C, Riley R, Merrill A Jr. (1991) "Inhibition of sphingolipid biosynthesis by fumonisins: implications for diseases associated with Fusarium monliforne." J Biol Chem 266: 14486; Yoo H S, Norred W P, Wang E, Merrill A H Riley R T (1992) "Fumonisin Inhibition of de Novo Sphingolipid Biosynthesis and Cytotoxicity Are Correlated in LLC-PK1 Cells." Toxicol Appl Phaarmacol 114: 9-15) It is likely that inhibition of this pathway accounts for at least some of fumonisin's toxicity, and support for this comes from measures of sphinganine:sphingosine ratios in animals fed purified fumonisin (Wang E, Ross P F, Wilson T M, Riley R T, Merrill A H (1992) "Increases in Serum Sphingosine and Sphinganine and Decreases in Complex Sphingolipids in Ponies Given Feed Containing Fumonisins, Mycotoxins Produced by Fusarium moniliforme." J Nutr 122: 1706-1716). Fumonisins also affect plant cell growth (Abbas H K, Boyette C D (1992) "Phytotoxicity of fumonisin B.sub.1 on weed and crop species." Weed Technol 6: 548-552; Vanasch M A J, Rijkenberg F H J, Coutinho T A (1992) "Phytotoxicity of fumonisin B.sub.1, moniliformin, and t-2 toxin to corn callus cultures." Phytopathology 82: 1330-1332; Vesonder R F, Peterson R E, Labeda D, Abbas H K (1992) "Comparative phytotoxicity of the fumonisins, AAL-Toxin and yeast sphingolipids in Lemna minor L. (Duckweed)." Arch Environ Contam Toxicol 23: 464-467). Kuti et al. "Effect of fumonisin B1 on virulence of Fusarium species isolated from tomato plants." (Abstract, Annual Meeting American Phytopathological Society, Memphis, Tenn.: APS Press 1993) reported on the ability of exogenously added fumonisins to accelerate disease development and increase sporulation of Fusarium moniliforme and F oxysporum on tomato.
The toxicity of fumonisins and their potential widespread occurrence in food and feed makes it imperative to find detoxification or elimination strategies to remove the compound from the food chain.